Path monitoring is important in networking. Path monitoring typically monitors a network for faults, and whenever faults do occur, network traffic is moved out of the faulty nodes/links to other normal nodes/links. The monitoring and mitigation ensures that a network work is highly available for sending data traffic even through some nodes/links are at fault. Bidirectional Forwarding Detection (BFD) is one approach for detecting path faults in traditional networks. With BFD, paths (e.g., pseudo-wire, PW) between nodes are monitored. The protocol periodically exchanges keep-alive packets between peers. So long as a node receives these packets from its peer, the connection is assumed to be up. If a node fails to receive a certain number of packets within a specific period (say 3 packets within 10 milliseconds), then the node will assume that the connectivity to the peer is lost on that path and will begin restoration action.
Software-defined networking (SDN) is a network architecture that aims at decoupling control plane functions from data plane functions such that separate apparatuses may be utilized for different functions. In the SDN architecture, network intelligence and states are logically centralized, and the underlying network infrastructure is abstracted from the applications. As a result, networking may be simplified and new applications become feasible. For example, network virtualization can be accomplished by implementing it in a software application where the control plane is separated from the data plane. Also, a network administrator of a SDN system may have programmable central control of network traffic without requiring physical access to the system's hardware devices. With these benefits, SDN architecture based systems (referred to as SDN systems or SDN networks exchangeably herein below) are gaining popularity among carriers and enterprises.
With both of SDN and path monitor being preeminent in networking, it is desirable to be able to implement path monitoring in a SDN system.